The invention pertains to communication networks in general and in particular to system and method for providing fault tolerance in an Ethernet based network communication system.
Communications networks typically include multiple nodes which communicate with each other over communications links. It is useful to think of the nodes as separate from the communications links, since they are often provided, maintained, and operated by different organizations and generally include and/or are coupled to termination devices actually utilizing the data or information communicated through the network. Each node in a network may include or be coupled to one or more computers or other information processing system, such as a telephony device, generically referred to herein as the xe2x80x9cnode computerxe2x80x9d, for performing a variety of tasks. Each node can communicate directly with one or more other nodes through communications links, which might be implemented with wires, optical fiber, radio transmissions, and/or some combination of these. Each link is often terminated at each end with an interface device, such as a modem or network interface card (NIC), which converts the signals from the associated node computer into and from a format suitable for the particular type of link. The information to be communicated between nodes can be generically referred to as xe2x80x9cuser dataxe2x80x9d, and it allows the various nodes to perform their functions in a distributed manner. The standard industry term xe2x80x9cuser dataxe2x80x9d is a carryover from the early days of computers, and does not imply that a human user must be involved. The content of user data is typically independent of the type of communications links being used.
It is desirable for any node in a network to be able to communicate a user message (i.e., a quantity of user data) to any other node. The most direct way of accomplishing this is to provide a separate link from every node to every other node, and let the transmitting node select the proper link for a given message. However, if the network has very many nodes, the number of links required would be prohibitively expensive. To avoid this problem, many networks allow a message to be passed from node to node, or via some other form of shared use link, until the message reaches its final destination. This greatly reduces the number of links needed to send a message from any node to any other node. In xe2x80x9cringxe2x80x9d networks (the nodes are connected in a loop), each node will typically have only two links, connecting it to two other nodes, and every message is simply passed around the loop until it reaches its destination node.
In a typical network, every user node is assigned a network xe2x80x9caddressxe2x80x9d and every message contains the address of its destination node. Nodes have the capability to examine the address of a received message, keep and process the message if it sees its own address, or forward the message to another node if it does not see its own address.
While most conventional network links are xe2x80x9chardxe2x80x9d links (copper wire or fiber-optic), network communications over radio links have also been developed. Large scale microwave networks may be deployed using millimeter wave technology, such as shown in the above referenced patent application entitled xe2x80x9cCOMMERCIAL NETWORK BASED ON POINT TO POINT RADIOSxe2x80x9d involving the deployment of hundreds of links in a service area. Each of these links may carry customer traffic for the services provided by a telecom operator or other service provider, i.e., the traffic can be Internet e-mails, phone calls, video conference calls, etc. and/or these links may carry customer traffic for the services of another type of service provider, such as a computer network service provider, or even a private system""s traffic.
One protocol for providing communication among nodes in a network is the Ethernet networking system. Ethernet protocol defines a shared bus topology in which all nodes on a network generally have access to all data placed on the network. While Ethernet is a common and convenient networking system, it lacks an effective mechanism for link fault tolerance. Therefore, the existence of a faulty connection could disrupt communication on a network without there being a built in remedy to address the disruption.
Where the network is entirely contained within a secure environment, a shared bus topology may not be problematic. However, where it is desired to protect the security and privacy of data associated with each node on a network from access by any other node on the network, standard Ethernet operation could present the problem of network users having access to data which is not intended or authorized.
Therefore, there is a need in the art for establishing link fault tolerance in an Ethernet or other shared link based networking system.
There is a further need in the art for a mechanism to provide security and privacy for data associated with a particular node in an Ethernet environment.
These and other objects, features and technical advantages are achieved by a system and method which conducts communication between a plurality of nodes in a network employing Ethernet or other form of Open Systems Interconnection (O.S.I.) layer two switching in a point to point transmission scheme. Routers or other form of layer three network data routing device may be advantageously incorporated at selected points in the network to provide redundant communication paths and thereby enable fault tolerance and prevent infinite looping of messages through the network. This network configuration may be referred to as consecutive point transmission. In this application, when no specific O.S.I. level is identified in connection with the term xe2x80x9cswitchxe2x80x9d, the term xe2x80x9cswitchxe2x80x9d refers to a layer two switch.
In a preferred embodiment, the network comprises nodes which are serially connected to form a complete ring wherein each node in the ring communicates with immediately neighboring nodes in both directions around the ring. This configuration preferably comprises routers at opposed ends of the ring network to control the transmission of messages within the network. This configuration provides fault tolerance by presenting alternative paths around the ring for any particular transmission.
In a preferred embodiment, communication between nodes in the communication network is achieved via wireless radio links preferably in the millimeter wave band to provide bi-directional communication between serially linked nodes. Alternatively, wired connections incorporating copper wire or fiber optic cable may be employed to provide for bi-directional communication between network nodes. In this application, the term xe2x80x9cserially linkedxe2x80x9d does not refer to a communication format or protocol, but rather to a physical connection configuration of a sequence of network nodes. This may alternatively be described as a chain or daisy chain of nodes in direct sequence. A ring network is one particular network configuration of such a set serially linked nodes.
In a preferred embodiment, a number of O.S.I. layer two protocols may be employed for communication between nodes within a network, whether in a ring or other configuration. Such protocols include but are not limited to: Ethernet and token ring. Preferably, the layer two protocols appropriately cooperate with protocols in different layers within the open systems interconnection model.
A preferred embodiment ring configuration of a consecutive point transmission system employing radio Ethernet communication presents the advantage of inherently providing for redundant paths between any two nodes in the network. This feature would be absent in a straight line point to point transmission system. In a straight line configuration, a fault in a link between nodes would leave parts of the network isolated from each other barring the introduction of an extrinsic link to compensate for the malfunctioning link. (Generally, the deployment of Ethernet, or other O.S.I. layer two protocol, in a ring configuration under normal circumstances, presents the problem of a an infinite communication loop, or communication xe2x80x9cshort circuitxe2x80x9d, being created. Specifically, messages or data packets transmitted from a node in a particular direction around the ring could circle around the ring indefinitely ultimately resulting in network performance degradation or failure due to endless transmission of these messages or data packets. This is a known property of Ethernet and is one reason why Ethernet is generally not used for communication between nodes in a ring network.
In a preferred embodiment of the present invention, the problem of xe2x80x9cinfinite loopxe2x80x9d transmission is resolved by deploying IP or other O.S.I. layer three routers at strategically located points in the network. The routers may serve as nodes by themselves or be located within nodes having other communication equipment. Preferably, two router nodes (the nodes containing routers) are placed at opposed ends of the ring network thereby separating the ring into two substantially equal halves for optimal operation. Alternatively, the routers need not be placed at opposed ends of the ring but could be placed in a range of different possible locations within the ring and still provide the network with the features of fault tolerance and infinite loop prevention. In an alternative embodiment, more than two routers could be deployed within the ring network and placed in a range of possible locations within the network so as to optimize control over message traffic through the network.
In a preferred embodiment, at least two different types of routers have specific and separate functions. A first router, referred to herein as an access router, preferably operates as the communications center of the entire network. The second router, referred to herein as an end router, preferably operates to replace part of the function of the access router if there is a malfunction in a communication link connecting two nodes in the network. In an alternative embodiment, where more than two total routers are employed within a ring network, there would preferably still be just one access router but the number of end routers would increase. In yet another alternative embodiment, there could be more than two types of routers in the network.
Preferably, all nodes communicate with the outside world and with each other by having all their communication routed to the access router first, wherein the access router then proceeds to communicate the transmitted information back onto the network toward the designated recipient for a recipient located within the network, or alternatively onto a wide area network such as the Internet where the recipient is located remotely from the consecutive point network. This applies even to nodes in the network which are in the same xe2x80x9chalfxe2x80x9d of the ring, or otherwise stated, which are not separated by router nodes. It is noted here that nodes which are not designated as xe2x80x9crouter nodesxe2x80x9d are preferably connected to the network by switches employing Ethernet switching or other form of O.S.I. layer 2 switching.
The nature of the Ethernet standard is generally to provide open access by all parties connected to a network to all data placed on the network. This feature presents a problem when present on a network where it is desired to protect the security and privacy of data belonging to individual users, or customers, from access by the outside world in general (such as from the Internet connection to the Access router) and by other customers within the ring network, whether on the same or different nodes.
In a preferred embodiment of the present invention, a combination of virtual LANs (VLANs) and sub-networks operate to protect the privacy of data of individual customers. The VLANs operate at O.S.I. layer two, and the sub-networks at O.S.I. layer three. Employing the VLANS and the sub-network structure, customers conduct all communication by both transmitting and receiving information along their respective private VLANs between their respective ports on a network node and the Access router of the ring network. The Access router then appropriately routes the data to the intended destination. If the communication is between two customers within the ring network, the Access router receives the information on the sender""s VLAN, transfers it to the receiver""s VLAN within the Access router, and then transmits the information along the ring network within the receiver""s VLAN in a manner which makes the transmitted information unreachable by all except the intended recipient. The Access router thereby preferably operates as a bridge between the various customer-specific VLANs. It is noted that, in a preferred embodiment, a plurality of VLANs and subnetworks can co-exist on the same physical network and the same internodal communication links.
The use of Ethernet creates a flexibility and ease of communication which is advantageous for most purposes. Under certain circumstances, the ability of customers on nodes within the preferred embodiment ring network to communicate directly with each other via the shortest path might be desirable. However, in the preferred embodiment, it is desired that all communication, including that occurring between customers located within the ring network, be routed through the Access router for purposes of monitoring, control, and metering. It is desired that the service provider which operates the ring network and the Access router be able to meter the communication occurring on any part of the network, including that between customers on the network, so that appropriate billing be conducted.
The deployment of VLANs and subnetworks effectively forces all communication on the network to pass through the Access router before it can reach an intended recipient. Accordingly, as the Access router performs the required bridging function to transfer information from one customer VLAN to another, appropriate measurement of characteristics, including but not limited to the data volume, communication speed, and traffic type (e.g. FTP, voice over IP, HTTP) of the communication being transacted may be recorded for both billing purposes and system performance monitoring purposes.
In a preferred embodiment, the links between the nodes in the inventive communication network are provided by radio frequency transmissions thereby creating a wireless network. Connections between components located within any one node are preferably wired links but alternatively may be accomplished by wireless connections.
Therefore, it is an advantage of the present invention that fault tolerance can be implemented in a network employing Ethernet switching.
It is a further advantage of the present invention that infinite loop transmission of messages is avoided employing the features of the present invention.
It is a still further advantage of the present invention that security can be provided for each of a plurality of end users of the communications network which permits only a designated recipient to view a particular message transmission.
It is a still further advantage of the present invention that control, monitoring, and metering of network usage by various end users on the network can be provided by forcing all communication to be transmitted through an Access router before being directed to an intended recipient on the inventive network or on the Internet.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.